Until recently, the cathode ray tube ("CRT") has been the primary device for displaying information. While having sufficient display characteristics with respect to color, brightness, contrast and resolution, CRTs are relatively bulky and power hungry. In view of the advent of portable laptop computers, the demand has intensified for a display technology which is lightweight, compact, and power efficient.
One available technology is flat panel displays, and more particularly, Liquid Crystal Display ("LCD") devices. LCDs are currently used for laptop computers. However, these LCD devices provide poor contrast in comparison to CRT technology. Further, LCDs offer only a limited angular display range. Moreover, color LCD devices consume power at rates incompatible with extended battery operation. In addition, a color LCD type screen tends to be far more costly than an equivalent CRT.
In light of these shortcomings, there have been several developments recently in thin film, Field Emission Display (FED) technology. In U.S. Pat. No. 5,210,472, commonly assigned with the present invention, a FED design is disclosed which utilizes a matrix-addressable array of pointed, thin-film, cold emission cathodes in combination with a phosphor luminescent screen. Here, the FED incorporates a column signal to activate a single conductive strip within the cathode grid, while a row signal activates a conductive strip within the emitter base electrode. At the intersection of both an activated column and an activated row, a grid-to-emitter voltage differential exists sufficient to induce a field emission, thereby causing illumination of the associated phosphor of a pixel on the phosphorescent screen. Extensive research has recently made the manufacture of an inexpensive, low power, high resolution, high contrast, full color FED a more feasible alternative to LCDs.
In light of its inexpensive, low power, full color, high resolution, high contrast capabilities, several new applications of FED technology are currently being explored. One area of interest is utilizing FEDs in the projection of images. For example, in the area of video camera technology, where a viewfinder displays the captured image within a channel designed for close viewing, there has been a growing interest in projecting the captured image onto a background. Presently, FEDs display images by illuminating a pixel on the phosphorescent screen. Nonetheless, the energy generated by the FED in the process of illumination is insufficient to project an image from the display onto a background.